1998-02-18_PERMIT FILE - C1981010A

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Even though data are scarce for other major shrub species, it is logical to extend the effects of dense oak brush stands to the other overstory species as well. Therefore a standard based upon naturally occurring stem densities typical of the mine site is inappropriate. In 1979, Trapper Mine Environmental staff initiated a field investigation to examine the correlation between varying shrub densities and use by sheep, deer and elk. The goal was to develop a regression equation which could then be used to establish a revegetation shrub density standard. Data from the 1979 study are presented in Table 4.4-11. The following linear regression equation was developed from the density-use data collected in the fall of 1979: Yi= R o + a 1 Xi Y= 57.89 + (-.2174)(x) where: (i 1= SSxv SSx= E Xi2- (E Xi)2/n = 177738.63 SSx SSxy= E (Xi Yi) - (E Xi)(E Yi)/n =-38648.84 SSy= E Yi2- (E Yi)2/n = 16369.79 R o = Y- p 1X Y= 31.89, X= 119.58 A calculated correlation coefficient (r2) for the above regression equation is -.51. For biological relationships, an r2 greater than +.5 is considered acceptable. In this case, r2 denotes an inverse relationship, i.e. as stem density increases, animal use (sheep) decreases. In the 1979 study, scat from three species of ungulates were inventoried within circular 10 sq. meter plots. Of the three species (elk, deer and sheep) it was found that relationships of stem densities and/or stem diameters when compared to total sheep pellets gave the best r2 value. In order to analyze a revegetation shrub density standard for range sites A and B, the above linear regression equation was used to generate Table 4.4-12. This table shows that if the stem densities that existed prior to mining in range site A and B were reestablished, it would result in a decrease in the potential use by livestock (sheep). The level of use would be 31.9% below the maximum attainable based on the regression equation. In addition, the cost would be about $81,500 per acre if all shrubs to meet this density were obtained from transplants. Therefore, Trapper Mine will establish shrub clumps at no less than 1.6 acres in extent on range sites A and B. Distance between shrub clumps will not generally exceed 1,400 feet. No shrubs will be seeded on range site C where the primary postmining land use will be domestic grazing. A determination of successful shrub revegetation will be based upon the following 3 points: 1) Shrub standards will not be set for range site C (big sagebrush-grass range site). Range site C is primarily domestic grazing land. Any use by deer or elk is purely incidental. This type of use occurs 4-113 Revision: i/= Approved: